1.the act of fat people or skinny doing it in the flaps(rolls) by being jerked off in on flaps or scissoring in the fat flap sex is a way some fat people show there affection since it's hard to find the lovers genitals.

(brandon) man i made sweet love to my boyfriend
(adam) i don't even want to know shut up
(brandon) man we did each other in the flap
(adam) so you had flap sex
(brandon) yeah
(adam) nice